21779808 has 48 divisors (see below), whose sum is σ = 57435840. Its totient is φ = 7226496.

The previous prime is 21779803. The next prime is 21779809. The reversal of 21779808 is 80897712.

It is a tau number, because it is divible by the number of its divisors (48).

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21779808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21779803) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29103 + ... + 29841.

It is an arithmetic number, because the mean of its divisors is an integer number (1196580).

Almost surely, 2^21779808 is an apocalyptic number.

It is an amenable number.

21779808 is an abundant number, since it is smaller than the sum of its proper divisors (35656032).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21779808 is a wasteful number, since it uses less digits than its factorization.

21779808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1059 (or 1051 counting only the distinct ones).

The product of its (nonzero) digits is 56448, while the sum is 42.

The square root of 21779808 is about 4666.8841854068. The cubic root of 21779808 is about 279.2659685445.

The spelling of 21779808 in words is "twenty-one million, seven hundred seventy-nine thousand, eight hundred eight".